Environmental Molecular Sciences Laboratory

About: Environmental Molecular Sciences Laboratory is a facility organization based out in Richland, Washington, United States. It is known for research contribution in the topics: Mass spectrometry & Ion. The organization has 1471 authors who have published 3010 publications receiving 169961 citations.

Interaction of Molecular Oxygen with the Vacuum-Annealed TiO2(110) Surface: Molecular and Dissociative Channels

Abstract: vacancy population), presumably due to dissociative filling of the vacancy sites in a 1:1 ratio. Above a coverage of 4 10 13 molecules/cm 2 , a first-order O2 TPD peak appears at 410 K. Oxygen molecules in this peak do not scramble oxygen atoms with either the surface or with other coadsorbed oxygen molecules. Sequential exposures of 16 O2 and 18 O2 at 120 K indicate that each adsorbed O2 molecule, irrespective of its adsorption sequence, has equivalent probabilities with respect to its neighbors to follow the two channels (molecular and dissociative), suggesting that O 2 adsorption is not only precursor-mediated, as the sticking probability measurements indicate, but that all O2 molecules reside in this precursor state at 120 K. This precursor state may be associated with a weak 145 K O2 TPD state observed at high O2 exposures. ELS measurements suggest charge transfer from the surface to the O2 molecule based on disappearance of the vacancy loss feature at 0.8 eV, and the appearance of a 2.8 eV loss that can be assigned to an adsorbed O2 - species based on comparisons with Ti-O2 inorganic complexes in the literature. Utilizing results from recent spin-polarized DFT calculations in the literature, we propose a model where three O2 molecules are bound in the vicinity of each vacancy site at 120 K. For adsorption temperatures above 150 K, the dissociation channel completely dominates and the surface adsorbs oxygen in a 1:1 ratio with each vacancy site. ELS measurements indicate that the vacancies are filled, and the remaining oxygen adatom, which is apparent in TPD, is transparent in ELS. On the basis of the variety of oxygen adsorption states observed in this study, further work is needed in order to determine which oxygen-related species play important roles in chemical and photochemical oxidation processes on TiO2 surfaces.

Proteomics by FTICR mass spectrometry: top down and bottom up.

Abstract: This review provides a broad overview of recent Fourier transform ion cyclotron resonance (FTICR) applications and technological developments relevant to the field of proteomics. Both the "bottom up" (peptide level) and "top down" (intact protein level) approaches are discussed and illustrated with examples. "Bottom up" topics include peptide fragmentation, the accurate mass and time (AMT) tag approach and dynamic range extension technology, aspects of quantitative proteomics measurements, post-translational modifications, and developments in FTICR operation software focused on peptide and protein identification. Topics related to the "top down" approach include various aspects of high mass measurements, protein tandem mass spectrometry, methods for the study of protein conformations, and protein complexes as well as advanced technologies that may become of practical utility in the coming years. Finally, early examples of the integration of both FTICR approaches to biomedical proteomics applications are presented, along with an outlook for future directions.

Hepta‐ and Octacoordinate Boron in Molecular Wheels of Eight‐ and Nine‐Atom Boron Clusters: Observation and Confirmation

Abstract: Clusters of atoms can adopt different atomic arrangements from bulk materials. They often exhibit novel structures and properties, which provide opportunities for a new types of chemical bonding and stoichiometry. Herein we report experimental and theoretical evidence that 8- and 9-atom boron clusters are perfectly planar molecular wheels, with a hepta- or octacoordinated central boron atom, respectively, despite the predominance of three-dimensional structures normally found in bulk boron and its compounds.

Human Plasma N-Glycoproteome Analysis by Immunoaffinity Subtraction, Hydrazide Chemistry, and Mass Spectrometry

Abstract: The enormous complexity, wide dynamic range of relative protein abundances of interest (over 10 orders of magnitude), and tremendous heterogeneity (due to post-translational modifications, such as glycosylation) of the human blood plasma proteome severely challenge the capabilities of existing analytical methodologies. Here, we describe an approach for broad analysis of human plasma N-glycoproteins using a combination of immunoaffinity subtraction and glycoprotein capture to reduce both the protein concentration range and the overall sample complexity. Six high-abundance plasma proteins were simultaneously removed using a pre-packed, immobilized antibody column. N-linked glycoproteins were then captured from the depleted plasma using hydrazide resin and enzymatically digested, and the bound N-linked glycopeptides were released using peptide-N-glycosidase F (PNGase F). Following strong cation exchange (SCX) fractionation, the deglycosylated peptides were analyzed by reversed-phase capillary liquid chromato...

An accurate mass tag strategy for quantitative and high-throughput proteome measurements.

Abstract: We describe and demonstrate a global strategy that extends the sensitivity, dynamic range, comprehensiveness and throughput of proteomic measurements based upon the use of polypeptide''accurate mass tags'' (AMTs) produced by a global protein enzymatic digestion. The two stage strategy exploits Fourier transform ion cyclotron resonance mass spectrometry (FTICR) to first validate polypeptide AMTs for a specific organism, tissue or cell type from''potential mass tags'' identified using conventional tandem mass spectrometry (MS/MS) methods, providing the basis for subsequent measurements without the need for MS/MS. A single high resolution capillary liquid chromatography separation combined with high sensitivity, high resolution and accurate FTICR measurements is shown to be capable of characterizing polypeptide mixtures of significantly more than 105 components with mass accuracies of < 1 ppm, sufficient for broad protein identification using AMTs. Attractions of the approach include the capability for automated high confidence protein identification, broad and unbiased proteome coverage, the capability for exploiting stable-isotope labeling methods to realize high precision for relative protein abundance measurements, and the potential for study of mammalian proteomes when combined with additional sample fractionation. The strategy is demonstrated by selected examples using Saccharomyces cerevisiae, Deinococcus radiodurans, and mouse melanoma cells.